INTRODUCTION. 3 



rous uncommon plants in the space of a few yards, 

 The spots, therefore, most likely to harbour plants, 

 should be carefully sought and diligently explored. 



It has been a disputable matter whether geological 

 formations exercise any remarkable influence upon 

 vegetation, and DE CA^DOLLE was of opinion that 

 they did not, nor do I believe that the geological age 

 of any strata are indicated by its plants ; but as 

 Dr. F. U^GER has well remarked, in his Flora of the 

 Western Tyrol, " It cannot be denied that calcareous 

 strata possess a flora very different from that of all 

 others. ZUCCARLNT and SIEBER observed this fact, 

 on the south side of the Alps ; in the Carpathian 

 mountains WAHLENBERG counted forty-three plants 

 which belong to a calcareous soil ; and he made the 

 same observation in Sweden. On the new continent 

 MAETITTS was struck with the same facts, in the 

 neighbourhood of the river of San Francisco, where 

 the chalk begins ; he there perceived vegetation to 

 assume a peculiar character, remarkable for the pre- 

 dominance of certain forms." Limestone, then, 

 seems a very congenial pabulum for many plants, 

 which if not entirely confined to it, abound with 

 greater luxuriance there, and the presence of a cal- 

 careous soil may be inferred by the presence of such 

 species, while they may be looked for with great 

 probability, and often certainty, on the margin of 

 limestone quarries. Such plants are, 



Clematis Vitalba Viola hirta 



Draba incana Silene nutans 



rnuralis 



Hutchinsia petraea 



Anthyllis vulneraria 

 Hippocrepis comosa 



* UNGER, on the influence of the nature of the soil upon the distribution 

 of vegetables, in Mag. Nat. Hist., vol. ii., N. S., p. 77. 



B 2 



